1. Field of the Invention
The present invention relates to a pressing method, a pressing mechanism and a resin molding device that utilize pressure of working fluid.
2. Description of the Background Art
A pressing mechanism conventionally used in a resin sealing device, which introduces molten resin into a cavity to resin-seal an electronic component in a chip form in a substrate, or in other resin molding devices is of the type that has a base freely movable up and down. The base is provided with a cylindrical hole through which a piston is inserted via a spring, and the entire base is moved up and down by hydraulic pressure. In the case of the resin molding device, a plunger that is attached to an end of the piston is pushed up to press molten resin to make it enter the cavity, where the molten resin is hardened for resin molding.
The conventional pressing mechanism, however, poses the following problems. First, the hydraulic pressing mechanism requires piping for hydraulic oil. The oil may leak out of the piping, contaminating the surrounding area. Such contamination becomes a serious problem especially in the assembly process of electronic components like semiconductor devices.
In addition, to use a spring to transmit the movement of the base to the piston, the spring should have a large diameter to receive the pressure. This makes it difficult to downsize the pressing mechanism. Usually such a problem is fatal in the resin molding device employing a plurality of plungers, as it becomes difficult to downsize the device itself.
Further, variation in spring characteristics is likely to cause variation in the way of pushing up the piston by the pressing mechanism. In the resin molding device employing a plurality of plungers, such variation is usually accompanied by variation in fluidity of the molten resin, making it difficult to push up the pistons in a uniform manner. This may create void or surface sink in a molded article, thereby degrading the quality thereof.